: The occurrence characteristics, water body type, occurrence conditions, hydrogeological conditions and stratum structure of the weak and weathered thin bedrock, are first analyzed in a research coal field. Through similar material simulation model tests, the failure law of overburden and the developmental characteristics of the "Three Belts" in the conditions of mining under the thin bedrock in the study area are obtained. When coal mining is 3 meters thick, the developmental height of the caving zone and the water flowing fractured zone is calculated as 11.5 meters and 42 meters, respectively. Based on the geological and mining conditions, through discrete element numerical simulation, the overburden failure law and characteristics of strata pressure behaviors were studied under the weak and weathered composite roof during coal mining. The results show that under the conditions of the weak and weathered thin bedrock working face, the fracture length of old roof pressure will decrease, the abutment stress in front of the working face will distribute within a range of 12 meters, the peak point of abutment pressure in front of the working face will vary from 4 to 12 meters. This is smaller than that of the working face of thick bedrock, but the strata behaviors of the working face are obvious. The developmental height of the caving zone and the water flowing fractured zone is calculated in different heights of coal seams. The influence degree of coal layer safety mining is evaluated; the appropriate water control measures have been submitted purposefully, in order to ensure safe mining.